In systems for payment of road tolls or road charges, a well-known method is to equip vehicles with a vehicle apparatus of some kind, often a transponder, the task of which is to effect the payment of the road toll or the road charge by communication with the system. Such vehicle apparatuses often communicate with the system by wireless means, for example via radio or infrared means.
In order to check that the vehicle on the roadway is equipped with a transponder and in order to be able to detect, identify and charge vehicles that are not equipped with a transponder, cameras or the like are often used for photographing vehicles on the roadway.
The images that are taken of vehicles can then be matched with the transponders from which signals have been received, and, on the basis of this information, it can then be determined in various ways which vehicles have not been equipped with transponders.
In order to be able to match vehicles and transponders, it is necessary to know the position of both the vehicles and the transponders. The position of the transponders can be obtained by means of their wireless communication with the system, for example by taking bearings. The position of the vehicles is obtained by means of the image or images, and by knowing where on the roadway the vehicles were located when the image was taken. On the basis of the positions of both the transponders and the vehicles that are known in this way, matching can be carried out, and vehicles without transponders can be found.
The position of the vehicles is thus obtained using the fact that it is known where the vehicles are located on the roadway when the images are taken, which is known as the images are taken when the vehicle passes by some type of apparatus, usually arranged in or at the side of the roadway, that triggers the taking of the image.
A problem in this connection is that the apparatus that triggers the taking of the image is expensive and difficult to maintain.